The invention relates to a rubber material for soundproofing, whereby the vulcanized rubber mixture consists of the following components, specifically
a rubber or rubber blend;
a heavy metal and/or its alloys and/or its oxides and/or it salts in the form of powder; as well as the conventional mixing ingredients.
A rubber material of the type specified above is known, for example from published patent document U.S. Pat. No. 3,652,360.
Soundproofing comprises both sound reduction and sound absorption. The property of reflecting the incident sound waves more or less extensively and permit them to pass through the material only to a minor extent is associated with the term sound reduction. In connection with sound absorption, the vibration energy of the sound is converted into thermal energy and thus irreversibly withdrawn from the vibration process. The rubber material is consequently required to have a high mechanical loss factor.
Now, against the background of the partial physical processes taking place in connection with sound insulation as described above, the problem is to provide a rubber material that, in the presence of a high weight (e.g. weight per unit of area), is characterized by
a low module of elasticity (E-module);
a low degree of stiffness, as well as
a high mechanical loss factor.
Said problem is solved by
a rubber mixture based on
chlorobutyl rubber (CIIR), bromobutyl rubber (BIIR), or acrylate rubber (ACM), each in the non-blended form, or
nitrile rubber (NBR) or styrene-butadiene rubber (SBR), both blended with epoxidized natural rubber (ENR), whereby
the rubber mixture comprises the following quantitative proportions:
Rubber or rubber blend heavy metal and/or its alloys 10% to 50% by weight
and/or its oxides and/or its salts 85% to 40% by wt. mixture ingredients 5% to 10% by wt.
A heavy metal of the 4th period of the elements of the secondary group is advantageously used, where, in turn, the 8th secondary group comprising iron (Fe), cobalt (Co) and Nickel (Ni) is of special importance. In the overall group of heavy meals specified above, their alloys and/or their oxides and/or their salts are useful components of the mixture as well. Of special importance is in this connection a substantially pure iron or an iron-carbon alloy (e.g. gray cast), or the iron oxide Fe3O4, which is a mixed oxide consisting of FeO and Fe2O3.
The quantitative ratio of NBR or SBR to ENR within the framework of the respective rubber blend amounts to from 50:50 to 90:10, in particular 70:30.
The heavy metal and/or its alloys and/or its oxides and/or its salts usefully have a grain size of from 10 to 80 xcexcm, in particular of 15 to 45 xcexcm, and in particular again of from 30 to 40 xcexcm.
The advantageous quantitative proportions of the rubber mixture are as follows:
Rubber or rubber blend 15 to 30% by weight
Heavy metal and/or its alloys and/or its oxides and/or its salts 80 to 60% by weight
The usual mixing ingredients 5 to 10% by weight.
The conventional mixing ingredients are in most cases vulcanizing agents (e.g. sulfur or sulfur donors), accelerators, carbon black, ZnO, as well as anti-ageing agents.
The rubber mixture as defined by the invention is advantageously produced by means of a method that is characterized by the following steps of the method:
The partial rubber mixture comprising the rubber or rubber blend as well as the conventional mixing ingredients is produced in an internal mixer.
By means of mastication with the help of a rolling mill, the rubber mixture is prepared for receiving the heavy metal and/or its alloys and/or its oxides and/or its salts.
The heavy metal and/or its alloys and/or its oxides and/or its salts are blended into the rubber mixture.
The total mixture is homogenized in the rolling mill.
The vulcanization of the homogenized total mixture is subsequently carried out by supplying heat to a suitable pressing mold, or by calendering with subsequent vulcanization.
A comparative test is described in the following. In that test, the two different rubber materials (A, B) based on BIIR differ from each other in the presence of the same sample size (plate with an surface area xe2x80x9cSxe2x80x9d of 0.09 m2 and a thickness xe2x80x9chxe2x80x9d of 3 mm) only in that the rubber material (B) contains 80% by weight Fe-powder, specifically with a grain size of from 30 to 40 xcexcm.
The measuring criteria and measured values are specified in the following table:
As compared to the material (A), the material (B) as defined by the invention does in fact have a 6-times higher E-modulus; however, of decisive importance in the present case is the comparison with steel, which has an E-modulus of 2.1xc3x97105 MPa. This means that the required low E-modulus has been achieved.
Furthermore, in connection with the problem specified above, as compared to the material (A), the rubber material (B) as defined by the invention is characterized by a higher weight by unit of area; lower stiffness (tension value), as well as by a higher mechanical loss factor in the presence of low inherent heating of the rubber material, because it was possible in that regard to raise the thermal conductivity by the Fe-powder. The increase in stressability and the thermal stability of the rubber material have consequently been achieved.